1. Field of the Invention
The invention relates to an oil collecting structure of a blow-by gas recirculation system (hereinafter called “PCV (positive crankcase ventilation) system” when appropriate) having an oil separator that separates oil mist (such as engine oil in the form of mist) from blow-by gases of an internal combustion engine installed on, for example, an automobile, wherein the blow-by gases from which the oil has been separated is fed to an intake system of the engine. In particular, the invention is concerned with measures for reducing the water content of the oil collected after being separated from the blow-by gases in the oil separator.
2. Description of the Related Art
An engine for an automobile is provided with a PCV system that serves to vent blow-by gas blowing into the crankcase through clearances between cylinders and pistons, and direct the blow-by gas to the intake system of the engine. Namely, the PCV system is arranged to feed the blow-by gas containing carbon monoxide, hydrocarbon and so forth, into combustion chambers, via the intake system of the engine, so as to prevent the blow-by gas from being released to the atmosphere.
An example of the PCV system as disclosed in Publication No. 6-45611 of examined Japanese Utility Model Application includes an oil separator. The oil separator separates oil mist contained in blow-by gas from the blow-by gas, and the oil thus separated is fed to an oil reservoir, such as an oil pan, while the blow-by gas from which the oil mist has been separated and removed is recirculated or fed back into the intake system of the engine.
In the oil separator, an oil separating mechanism for separating oil mist from the blow-by gas is housed. Various types of oil separating mechanisms are generally known which include one having a plurality of baffle plates placed inside the oil separator so as to provide a blow-by gas channel or channels in the form of a labyrinth, and one having one or more punching plate(s) and one or more baffle plate(s). While the blow-by gas is flowing through the interior of the oil separator, the gas hits inner walls of the baffle/punching plates under inertia, and oil mist is captured due to a so-called inertial collision effect.
As examples of the placement of the oil separator, laid-open Publication No. 61-39423 of unexamined Japanese Utility Model Application discloses an oil separator placed inside a cylinder head cover (hereinafter simply referred to as “head cover”) of the engine, and laid-open Publication No. 2003-27955 of unexamined Japanese Patent Application discloses an oil separator placed outside the head cover (for example, between right and left banks in a V-type engine).
The oil that has been separated from the blow-by gas by the oil separator passes through an oil collection path, such as an oil collection pipe, and is collected into the oil pan. The oil collection path is often placed at a position exposed to the outside air, under constraints of installation space, and the interior of the oil collection path thus positioned has a relatively low temperature (for example, about 5° C. in winter). Therefore, in the case where a large amount of water is contained in the oil that is separated by the oil separator and fed toward the oil pan to be collected, the water will not be evaporated, but will be collected along with the oil into the oil pan.
If the above-described situation continues, the water content of the oil stored in the oil pan may increase excessively. In this case, sludge may be produced due to the union or combination of the water and nitrogen oxides (NOx) contained in blow-by gas present in the crankcase. If the sludge is produced in large quantity, the oil may degrade, resulting in deterioration of its lubricating capability, or a blow-by gas ventilation/collection path, and the like, may be blocked by or clogged with the sludge, resulting in a situation where ventilation or collection of the blow-by gas cannot be smoothly performed.